Roller-bending machine for rounding sheet metal



Oct. 18, 1966 G. H. LAGHER 3,279,229

ROLLER-BENDING MACHINE FOR ROUNDING SHEET METAL Filed June 11, 1964 United States Patent Office 3,279,229 Patented Get. 18, 1966 3,279,229 ROLLER-BENDING MACHINE FUR ROUNDING SHEET METAL Gunnar Hjalmar Lagher, Fjalkinge, Sweden Filed June 11, 1964, Ser. No. 374,471 Claims priority, application Sweden, June 17, 1963, 6,654/63 6 Claims. (Cl. 72-170) This invention relates to roller bending machines for rounding sheet metal by passing the sheet between a driven feeding roll and a parallel adjustable or freely movable roll being adjacent to the feeding roll. A third roll is provided to make possible or to complete the bending action. Such known machines are useful for producing pipes having a longitudinal seam or joint, such as rain pipes (down pipes) but also semi-circular gutters etc. It i highly desirable to produce such pipes or gutters etc. as long as possible, say 15 feet. Normally the diameter has to be small, say 2 to 3 inches. Thus, said adjustable or movable roll must have a length at least equal to that of the tube to be produced and a diameter less than that of the tube. In other words, the adjustable roll must be extremely elongated. In the above numerical example, the ratio of length to diameter must exceed 90 or 60, respectively. Furthermore, if pipes of different diameters have to be produced, the adjustable roll must be replaced by another one having the appropriate diameter. Such exchangement of the roll is, normally, difficult with respect to bearings and support rolls of the adjustable roll.

The two remaining rolls referred to above should preferably have a diameter less than that of the adjustable roll so that their length-to-diameter ratio exceeds even the above values. Such elongated rolls are relatively weak or resilient with respect to forces in the transverse direction of the rolls, that is, when bending sheet metal, so that the roll gap between adjacent rolls will widen in the center region intermediary between the ends of the rolls so that the sheet metal tubes will have a smaller diameter at their ends than between the ends. It is wellknown that bending of sheet metal by means of rollers of small diameter and great length-to-diameter ratio requires considerable measures by which the machine is rendered more expensive and exchangement of the adjustable roll is made difficult.

According to the present invention, a roller bending machine as defined above is provided with electromagnetic means to produce a magnetic field passing in a substantially radial direction through those regions where the driven feeding roll and the adjacent adjustable roll are facing one another (and form a rolling gap for the sheet metal to be bent) so that these two rolls attract one another and subject a sheet passed therebetween to the force of attraction. For this purpose, the two rollers must comprise or consist of ferromagnetic material as is the case with well-known normal rollers of this kind.

The accompanying drawing is a merely schematical front view of an embodiment of a roller-bending machine according to the invention and is shown and described by way of example only.

A ferromagnetic sup-port 1 of steel is provided with two bearing bushings 1a, 1b of about semicylindrical form and substantially comprising ferromagnetic material. The bushings are welded upon the base portion of the support. Two driven lower rolls 2 and 3 of steel are rotatable in each of said bushings 1a and 1b respectively and engage or face a hollow steel roller 4. The support 1 is surrounded by an electromagnetical winding 5, the turn of which may consist of insulated copper or aluminum strips or bars 5a. If, in the longitudinal direction of the rolls and support 1 one winding only is provided, each turn extends around the whole longitudinal length of the support 1. The two rollers 2, 3 are driven through a gearing (not shown) from a common motor or manually. The adjust-able roll 4 is not driven but may be driven, if desired, from the same power source as the rolls 2, 3. The plate or sheet metal 6 to be bent has to be inserted in the roller gap between rolls 2 and 4 and is fed in the direc tion of the arrows so that it is bent in the way shown in the drawing.

In the example shown the roll 4 is not journalled and is rotated, by friction, by the rolls 2, 3 and sheet 6. The roll 4 may be guided, however, such that it is movable in the vertical direction only and, of course, is also rotatable. The roll 4 need not be hollow and may rotate in bearings which are either freely movable or (manually) adjustable in the vertical direction.

The winding 5 generates a magnetic field, and a dashed field line 7 is shown in the drawing which approximately is the center line or most effective line of the field. The components of the magnetic forces produced thereby may be understood by imagining that the field line 7 is substituted by an extended strong rubber string tending to contract. Thus, the upper roll 4 will be attracted towards the two lower rolls 2, 3 and is assisted by gravity. Owing to the combination of gravitational and magnetic forces, particularly if also the sheet 6 is ferromagnetic (as is nearly all kind of steel), the combined forces are suflicient to keep the roll 4 sufficiently pressed against the sheet if the sheet is not too rigid. Thus, bearings, pressingdow rollers etc. for roll 4 may be dismnsed with in most or all cases, so that it is easy to change the roll 4 if a roll of another diameter has to be used.

It should be kept in mind that the dashed line 7 of magnetic force is present in every cross-section of the cluster of rolls and, thus, counteracts the tendency of the center regions of the rolls to move away from one another so that the roller gaps between rolls 2 and 4 and between rolls 3 and 4 will remain substantially unchanged along the length of the rolls. Besides the segment bushings 1a, 1b prevent such tendency of the thinner rolls 2, 3 and substantially prevent any magnetic leakage or stray field between. support ll, bushings 1a, 1b and rolls 2, 3.

If the sheet 6 is ferromagnetic, e.g. sheet steel, it forms a magnetic shunt between rolls 2 and 3.. The shunting effect is negligible, however, and is even advantageous to some extent as it causes stronger attraction of the sheet towards the rolls 2, 3 than towards the roll 4 and, thus, compensates the loss of attraction of roll 4. Scrapers and/ or brushes (not shown) may be provided to cleanse the rolls 2 and 3 beyond the roll gaps.

Each bushing 1a, 111 may be replaced by a plurality of relatively short support rolls (not shown) distributed along the rolls 2, 3 or by one or more support rolls having the same length as the rolls 2, 3. Such support rolls of the rolls 2 and 3 must be magnetically interconnected either through support 1 or directly. For example, the support 1 itself may be replaced by one single support roll engaging the two rolls 2 and 3 and being surrounded by a stationary electromagnetic winding. It should be noted, that if the bushings lla, 1b are replaced by support rolls the reluctance of the magnetic circuit will be considerably increased so that the winding should comprise a considerably higher number of ampere-turns, if possible or suitable.

The magnetic field should be unidirectional, that is, the winding 5 or similar windings should preferably, though not necessarily, be D.C. fed. If a two way (whole wave) rectifier is used for supplying the winding with DC gained from A.C., smoothing of the rectified current normally is not required.

The magnetic forces are present along the whole length of the roll gaps. It may be desirable to increase the relative forces in the center region of the rolls and, perhaps, also at the front surfaces thereof where magnetic leakage may occur. Such nonuniform distribution of the magnetic force along the rolls may be achieved by relative increasement of the wall thickness of the central region of the rollers (if partially or wholly hollow) and/ or by relative increasement of the radial thickness of the bushings 1a, lb or the central body of the support 1.

The mutual attraction of the rolls caused by the magnetic and gravitational forces may be increased by producing a vacuum in the space defined by support 1 and rolls 2, 3, 4 as may be seen in the drawing. It would be extremely difficult to render such space vacuum-tight. For this reason a continuously or intermittently operating vacuum pump, preferably connected to a vacuum tank having a volume considerably exceeding that of said space, should be used to maintain the vacuum. A vacuurn of about one half or one third of normal atmospheric pressure or less would sufiice and may be obtained with simple means.

The rolls need not be circular and may be bending bars of an edging machine or profile curving machine for bending, say, tubes of rectangular or square cross-section or other profiled sheet metal.

Particularly when mounting the support )1 on a base magnetic shunting by said base should be avoided so that a steel base should not form a magnetic path along the chain line 8 or a similar line unless the reluctance of such path is high in comparison with that of the shunted path of the support 1.

What is claimed is:

1. A roller bending machine for rounding of sheet metal and comprising a driven feeding roll substantially consisting of ferromagnetic material, a parallel movable roll substantially consisting of ferromagnetic material and being adjacent to the feeding roll, a third parallel roll, all three roll engaging the sheet metal, and electromagnetic means to produce a magnetic field passing substantially radially through those regions where the driven roll and the adjacent movable roll are facing one another so that these two rolls attract one another and subject a sheet passed therebetween to the force of attraction.

2. A machine according to claim 1 wherein also the third parallel roll is adjacent to the movable roll such that the magnetic field penetrates the three rolls in succession and in a substantially radial direction within those regions where the rollers are facing one another.

3. A machine as claimed in claim 2 wherein the first roll, and the third roll are journalled on a stationary support of ferromagnetic material which interconnects the two rolls magnetically along their longitudinal direction so that said support in series with the three successive rolls forms a substantially closed magnetic circuit.

4. A machine according to claim 3 wherein said support is provided with electrical windings which in operation produce said magnetic field.

5. A roller bending machine for rounding of sheet metal and comprising two driven lower rolls of ferromagnetic material, an upper third roll of ferromagnetic material which is movable parallel to itself in the vertical plane of the axis of this roll and is parallel and adjacent to each of the two driven lower rolls, a fixed support comprising bearings for the two lower rolls and an electrical winding to produce a magnetic field passing through the support and the three rolls in succession to cause a force of attraction between the upper roll and the two lower rolls so that a sheet passed therebetween is also subjected to this force.

6. Machine according to claim 5 wherein each of said bearings comprises at least one bearing bushing segment comprising ferromagnetic material and extending in the longitudinal direction of the associated roll and directly engaging the bending work surface thereof such that a longitudinal region of said surface opposite to the third roll is free from the bearing bushing.

References Cited by the Examiner UNITED STATES PATENTS 2,325,523 7/1943 Lermont et a1 72-173 CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner. 

1. A ROLLER BENDING MACHINE FOR ROUNDING OF SHEET METAL AND COMPRISING A DRIVEN FEEDING ROLL SUBSTANTIALLY CONSISTING OF FERROMAGNETIC MATERIAL, A PARALLEL MOVABLE ROLL SUBSTANTIALLY CONSISTING OF FERROMAGNETIC MATERIAL AND BEING ADJACENT TO THE FEEDING ROLL, A THIRD PARALLEL ROLL, ALL THREE ROLLS ENGAGING THE SHEET METAL, AND ELECTROMAGNETIC MEANS TO PRODUCE A MAGNETIC FIELD PASSING SUBSTANTIALLY RADIALLY THROUGH THOSE REGIONS WHEREBY THE DRIVEN ROLL AND THE ADJACENT MOVABLE ROLL ARE FACING ONE ANOTHER SO THAT THESE TWO ROLLS ATTRACT ONE ANOTHER AND SUBJECT A SHEET PASSED THEREBETWEEN TO THE FORCE OF ATTRACTION. 